proxmox ve cluster upgrade to 7.x

Hi, We are running a 3-node cluster of Proxmox VE 6.3.3 with Ceph 15.2.8. We want to upgrade them to the newly released 7.x. Additionally, we want to remove a server from this cluster and add 3 more to them. In total, we would have 5 nodes. Currently, we are using Proxmox backup server 1.1.5...